The need to eliminate lead-based octane enhancers in gasoline has provided incentive for development of processes to produce high octane gasolines blended with lower aliphatic alkyl ethers as octane boosters. Supplementary fuels are being vigorously developed in the petroleum refining industry. Lower molecular weight alcohols and ethers such as isopropyl alcohol (IPA), isopropyl t-butyl ether (IPTBE), and diisopropyl ether (DIPE) are in the boiling range of gasoline fuels and are known to have a high blending octane number. They are useful octane enhancers. In addition, by-product propene (propylene) from which IPA and DIPE can be made is usually available in a fuels refinery, typically as a C3+ aliphatic stream rich in propene and propane. The petrochemicals industry also produces mixtures of light olefin streams in the C.sub.2 -C.sub.7 molecular weight range and the conversion of such streams or fractions thereof to alcohols and/or ethers can also provide products useful as solvents and blending stocks for gasoline.
Catalytic hydration of olefins to provide alcohols and ethers is established technology for production of the IPA and DIPE and is of significant commercial importance. Representative olefin hydration processes are disclosed in U.S. Pat. Nos. 4,334,890 (Kochar); 3,912,463 (Kozlowski et al.); 4,042,633 (Woods); 4,499,313 (Okumura et al.); 4,886,918 (Sorensen et al).
Olefin hydration employing medium pore and large pore zeolite catalyst is a known synthesis method. As disclosed he corresponding alcohol, essentially free of ether and hydrocarbon by-product. Acid resin catalysts such as "Amberlyst 15" may also be used for hydration of light olefins.
Production of ether from secondary alcohols such as isopropanol and light olefins is known. As disclosed in U.S. Pat. No. 4,182,914 (Imaizumi), DIPE is produced from IPA and propylene in a series of operations employing a strongly acidic cation exchange resin as catalyst. Recently, processes for the direct hydration of olefins to provide alcohols and ethers using medium pore shape selective metallosilicate zeolite catalyst, such as zeolite Beta have been disclosed in U.S. Pat. No. 4,857,664 (Huang et al.), incorporated by reference.
Adapting available refinery feedstock to produce these oxygenates simultaneously as octane enhancers can involve two different olefin hydration and etherification processes, i.e. propene hydration-etherification to give DIPE and IPA. Accordingly, a challenge is provided to explore these processes to discover how they may be integrated in a manner more beneficial to the production of high octane gasoline.
It is a main object of this invention to provide a process for production of ethers from lower olefin feedstock. It is another object of the present invention to provide an integrated process for the production of isoproanol and di-isopropyl ether in a continuous process, incorporating novel multi-stage reactor, product separation and fractionation techniques. A further object is to provide for conversion of isopropanol to di-isopropyl ether and propene.